Biorefineries process biological materials such as lignocellulosic biomass, or components derived therefrom, to extract and produce valuable materials. Lignin utilization is a key biorefinery concept, and efficient lignin utilization is important for improving the economic viability of biorefineries. Similarly, lignin can be obtained as a product of manufacturing pulp and paper from lignocellulosic biomass. Examples of lignins produced in the pulp and paper industry include kraft lignin, produced via the kraft process, lignosulfonates, produced, e.g. from the sulfite pulping process, alkali lignin, produced, e.g. from treating the black liquor from the soda process with acid, and low sulfonate alkali lignin. As with lignocellulosic biomass, these lignins may be further extracted, purified, and/or derivatized.
Often, the lignin from biorefiners and pulp and paper manufacturers is combusted to generate heat, steam, or electricity. This use of lignin provides minimal economic value as compared to other sources of heat, steam, or electricity such as natural gas. Further, new and more energy efficient plants can produce more lignin than they require for generation of heat, steam, and electricity. Thus, new technologies are needed to convert polymeric lignin produced by biorefiners and pulp or paper manufacturers into higher value products.
Lignocellulosic biomass is derived from agricultural wastes, forest residues and dedicated energy crops. In recent years, tremendous effort has been applied to develop methods for production of useful compounds from lignocellulosic biomass. However, one of the greatest limitations facing the economic viability of this technology is the recalcitrant nature of the lignocellulosic biomass, which resists breakdown and extraction of useful compounds. This resistance necessitates the use of treatment steps to enhance the accessibility to and depolymerization of the carbohydrate and lignin components present in the lignocellulosic biomass. Most treatment processes are comprised of thermo-chemical processes that utilize combinations of high temperatures and pressures, or dilute acids or alkalis, to open up the structure of the biomass. Such processes necessitate the use of specialized equipment and high-energy inputs.
Ionic liquids (ILs) recently emerged as innovative fluids for chemical processing. They are considered environmentally friendly solvents primarily due to their low volatility and their potential recyclability. Significantly, the use of ILs for the treatment of biomass has been shown to be a promising technology, allowing for the solubilization of crystalline cellulose from biomass under relatively mild conditions.
Although treatment of lignocellulosic biomass with ionic liquids has met with success, ionic liquids are expensive and the treatment process can be both energy and time intensive. As such, what is needed in the art is a process that produces lower cost ionic liquids and produces a supply of commercially useful, high-value, and renewable lignin-derived compounds to help improve overall process economics. The present invention provides compositions and methods that fulfill these and other needs.